1. Field of the Invention
The present invention relates to an apparatus for fixing a half mirror of an optical pickup for use in a disk player such as a DVD or a CD, which makes it possible to reliably fix a half mirror of an optical pickup to a housing.
2. Description of the Related Art
FIG. 8 shows an example of an optical pickup. This optical pickup has a half mirror HM disposed in an inclined state at midway in a light passage hole 2 formed in a housing 1. An objective lens OL and a collimator lens QWP, on the one hand, and a support member 4 with a photodiode PD, on the other hand, are respectively disposed at both ends of the housing 1 with the half mirror HM placed therebetween. Further, a semiconductor laser LD is provided on a side surface of the housing 1. A laser light is projected from the semiconductor laser LD onto a disk D such as a DVD or a CD through the half mirror HM, the collimator lens QWP and the objective lens OL, and the reflected light is received by the photodiode PD so as to read information recorded on the disk D.
As shown in FIGS. 9 to 11, a substantially L-shaped retaining seat 6 having an inclined side surface 6a and an inclined end surface 6b opposing orthogonal to each other is formed on one side surface 2a of the light passage hole 2. Further, a U-groove 7 is formed between the inclined side surface 6a and the inclined end surface 6b. A positioning seat 8 having an inclined side surface 8a flush with the inclined side surface 6a of the retaining seat 6 is formed on the other side surface 2b of the light passage hole 2.
As shown in FIGS. 9 to 11, the half mirror HM has the shape of a rectangular block, and is disposed so as to diagonally traverse the light passage hole 2 by causing its rear surface to abut against an end surface 2c of the light passage hole 2, its one end portion to abut against the inclined side surface 6a and the inclined end surface 6b of the retaining seat 6, and its other end portion to abut against the inclined side surface 8a of the positioning seat 8.
A technique for fixing the half mirror HM disclosed JP-A-8-111027 will be described with reference to FIGS. 9 to 11. In this technique, an ultraviolet curing adhesive agent 10 is injected by an injector 9 into three spots between the half mirror HM and the retaining seat 6, and between the half mirror HM and the positioning seat 8. Also, the adhesive agent 10 is injected by an injector 9 into the U-groove 7. Ultraviolet rays are then applied to the adhesive agent 10 to cure, thereby fixing the half mirror HM so as not to move unexpectedly in the left-and-right directions a and b, back-and-forth directions c and d, and vertical directions e and f.
With the above-described conventional structure, since the width t and the height h of the U-groove 7 are set to be 0.5 mm to 1 mm for example, and U-groove's opening area is small, there is a possibility that the adhesive agent 10 fails to be injected sufficiently into the U-groove 7 and flows out to the outside if the ultraviolet curing adhesive agent 10 is injected into the U-groove 7 at a time. In such case, the adhesive agent 10 is injected into the opening portion of the U-groove 7 only by an interval α, thereby rendering the fixation of the half mirror HM by the adhesive agent 10 unreliable.
Accordingly, it is conceivable to enlarge the width t and the height h of the U-groove 7. However, this may cause the ultraviolet curing adhesive agent 10 to be accumulated in the U-groove 7 in a relatively large quantity, and the half mirror HM may possibly be displaced from its predetermined position by being pulled by the shrinking force due to the curing of the adhesive agent accumulated therein.